My Raymarine C70 is off in locating my boat by 40-50 feet

I bought a 2005 Chaparral 290 with a Raymarine C70 GPS/Fishfinder/Radar. The GPS seems to be about 50-60 feet off in its placement of the boat. For example, when we're docked in our marina, the C70 shows us sitting on dry land. I heard the military had errors built into the system years ago, but I understood that the error has been removed. I sent the unit to Raymarine for check out and software upgrade. Is this a condition that I have to live with or is there an adjustment or setting that I can use to correct it?

Initially, a Raymarine C70 to my knowledge is a Multi-Function Display. It is not the model number for the GPS. The GPS could be something like a Raystar 125 whose output is then displayed at the C70. Having said this, then the necessary correction, check out and software upgrade should be performed on the actual GPS rather than on the display C70.

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The direction of the boat symbol is depending on the compass course from the autopilot. You will see that your GPS course (COG) and magnetig heading on the autopilot differs. Solution is to calibrate autopilot compass. Will advice you to not use course up, stick to north up or heading up.

If you have no chart card for your local area, you definitely need one! As far as getting various data on the screen, as long as it is available on the system, you can display different kinds of data by pressing the "data" button and then following the steps to add data to your readout.

If both plotter works but they have no comunikation
RESET the RL 70 AND L760
This is how it works
press the powerbutton when you have picture press the menu bottom
than systemsetup and than four seconds the menu bottom.
Do this on both plotter normaly after this it works again

Remove all wiring from 4000 head, hook up only 12V, if seatalk fail continues, it is the head. if seatalk fail goes away, hook in instruments one by one until the bad head is found. Seatalk is 12V red, Ground Screen(bare wire) and Data yellow (pulsing voltage).
good luck
847-746-0100
John Barry

Depending on your transducer type, you may have a liquid filled type that simply needs refilling. If this is the case check for leaks and get it redone. If not it could be transducer placement or cavitation under the hull.